CBSE Class 10 Answered

Solution

Here series is 114,109,104.......

Common differnce(d)109 - 114 = 104 - 109 = - 5.
                 Therefore given sequence is an A.P.
                 First term (a) = 114
                 Common difference (d) = - 5
                 For finding first negative term
                 Tn < 0
                 a + (n - 1)d < 0
                 114 + (n - 1)(- 5) < 0
               114 - 5n + 5 < 0
           119 - 5n < 0
            or   - 5n < - 119
            or   5n > 119
            or   n > 119/5
                  n > 23.8
                  Therefore first negative term is 24